Few flowers are as breathtaking as gladiolus. Whether growing outdoors or arranged in a stunning bouquet, these tall, striking flowers offer bright, beautiful color.
There are hundreds of varieties of gladiolus flowers available in just about every color and shape. Here's how to plant these summer-blooming beauties in your garden.
- Botanical Name: Gladiolus palustris
- Common Name: Gladiolus, glads, flag flower, sword lily
- Plant Type: Corm
- Mature Size: Two to five feet
- Sun Exposure: Full sun
- Soil Type: Medium-fertile, well-drained soil
- Soil pH: 6.0 - 6.5
- Toxicity: Toxic to humans, dogs, cats, and horses
Once they're planted in spring, gladiolus are a pretty low-maintenance flower, similar to tulips. Be sure to keep the soil consistently moist but not soggy during the spring and summer to ensure proper growth, then cut back on watering after blooms have faded. In zones 7 and warmer, gladiolus bulbs should be able to overwinter and regrow in the spring.
Cut gladiolus flowers for bouquets when the first blooms on a spike are beginning to open. Harvest cuttings in the cool early morning or early evening rather than the midday heat, making sure that at least four leaves are left on the plant so corms can fully develop.
Best Growing Conditions for Gladiolus
Gladiolus will grow best and display the brightest colors in a site with full sun and well-drained, sandy loam soil. If you have very heavy clay soil, mix in compost and soil conditioner to loosen it up and add fertility.
Gladiolus flowers grow from corms, bulblike tubers that store food for the plant underground. Plant gladiolus corms roughly six to 10 inches apart and two to six inches deep—larger corms will need to be planted deeper. Plant in groups of seven to 10 to create attractive groupings of blooms.
Gladiolus can be planted outdoors two weeks before your area's last frost date and should bloom by midsummer. To have additional waves of blooms through early fall, plant more corms every two weeks through early summer.
Types of Gladiolus
There are three main types of gladiolus to look for. Grandiflora hybrids are what you probably think of when you picture these striking blooms—tall spikes of big, beautiful flowers than can be as large as five inches across. They can grow up to four feet tall and may require staking to stay upright.
Dwarf grandiflora hybrids are smaller and more compact, making them ideal for container planting. They're typically cold hardy to zone 7. Nanus hybrids, another compact type, grow fewer flowers but still offer beautiful color. Hardy to zone 5, they're ideal for colder climates.
How to Propagate Gladiolus
Gladiolus can be propagated by division. As gladiolus plants grow, their corms or bulbs will reproduce by growing cormels, or smaller bulbs. It's best to wait until gladiolus plants are crowded in their planting site before dividing.
To propagate gladiolus, dig up the corms and cormels in fall, making sure to get them out of the ground before a hard freeze (28 degrees). You'll need a shovel, sanitized garden pruners, a paper bag, fungicide (also called bulb dust), and gardening gloves.
- Carefully dig around the entire gladiolus plant, making sure not to damage the corms. Once you've loosened the corms, lift up the entire plant from the top. Shake off soil, but avoid spraying the corms or getting them wet.
- Cut off the foliage about an inch above the top of the corms. Remove any remaining soil from the corms with your hands, keeping the husks intact. Lay out the corms in a single layer in a warm, dry place with good air circulation for two to three weeks to let them dry out.
- When the corms have dried, use your hands to remove the old (lowermost) corm growing from the base of the new corm and discard the old corm. You can also remove and save the small cormels, which grow on the outside of the old corm. Plant cormels each spring, and after two to three years, they'll be large enough to grow flowers.
- Place the dried gladiolus corms and cormels in a paper bag and add fungicidal powder (called bulb dust or dusting sulfur), then close the bag and shake well. This will protect the corms from diseases during dormancy.
- Label and store gladiolus corms in a breathable container like a paper, cloth, or mesh bag, or even an old pair of tights. Keep them in a cold, dark, dry place above freezing, like an unheated shed, basement, or garage.
- Replant corms and cormels in spring.
Common Problems With Gladiolus
If the spot your gladiolus is planted in is too wet or soggy, corms may rot or grow mold, viruses, or bacteria that can prevent growth or flowering. Choose a site with well-drained soil and plant undamaged corms.
In growing zones 6 and colder, corms may not be able to survive winter outdoors. Dig up corms in the fall and store them indoors in a cool, dark, dry place, then replant in fall.
Pests can damage corms and keep gladiolus from blooming. Rodents may eat or dig up bulbs so they don't grow at all, while insects like thrips will damage buds before they can bloom. Be cautious of this when planting.
Is gladiolus easy to care for?
Yes, gladiolus are easy to care for. After planting, they require minimal maintenance but reward gardeners with bright, colorful blooms.
How fast does gladiolus grow?
You can plant gladiolus bulbs in spring for summer flowers. Expect blooms 70 to 90 days after planting, depending on the variety.
Can gladiolus grow indoors?
Yes, gladiolus can be grown indoors in pots. Be sure to keep them in an east-facing or south-facing window where they will receive at least eight hours of sunlight each day.
University of California, Toxic Plants by Name